The purpose of these investigations is to determine if and how transfer RNA (tRNA) and/or other cellular factors involved in translation may be implicated in the regulation of both stable (rRNA and tRNA) and unstable (mRNA) synthesis. This study is being conducted in the following manner: 1. In vitro transcription of rRNA and identifiation and characterization of rRNA products. The rRNA cistrons of E. coli have been mapped and DNA enriched for these genes is being used as template. 2. Intracellular fate of tRNA. Specific labelling of tRNA enables us to follow the fate of tRNA under in vivo conditions. 3. Mutants. Temperature sensitive mutants altered in the regulatory processes involved in RNA synthesis are being examined. 4. In vivo regulation and control of E. coli rDNA in Proteus Mirabilis. 5. Tetracycline and the relaxed response to rRNA synthesis.